Resistor and conductor compositions which are applied to and fired on dielectric substances (glass, glass-ceramic, and ceramic) usually comprise finely divided inorganic powders (e.g., metal particles and binder particles) and are commonly applied to substrates using so-called "thick film" techniques, as a dispersion of these inorganic powders in an inert liquid medium or vehicle. Upon firing or sintering of the film, the metallic component of the composition provides the functional (resistive or conductive) utility, while the inorganic binder (e.g., glass, crystalline oxides such as Bi.sub.2 O.sub.3, etc.) bonds the metal particles to one another and to the substrate. Thick film techniques are contrasted with thin film techniques which involve deposition of particles by evaporation or sputtering. Thick film techniques are discussed in "Handbook of Materials and Processes for Electronics", C. A. Harper, Editor, McGraw-Hill, N.Y., 1970, Chapter 12.
One of the important characteristics of electrical resistors is their TCR. Many electrical resistors of the prior art, based on, e.g., precious metals, possess certain undesirable properties such as high TCR. See, e.g., D'Andrea, U.S. Pat. No. 2,924,540, issued Feb. 9, 1960 and Dumesnil, U.S. Pat. No. 3,052,573, issued Sept. 4, 1962.
More recently certain electrically conductive materials were found whose resistivity is virtually independent of temperature over a wide range of temperatures. See, e.g., Bouchard, U.S. Pat. No. 3,583,931, issued June 8, 1971 and Hoffman, U.S. Pat. No. 3,553,109, issued Jan. 5, 1971. Resistors based on the pyrochlore-related materials described in the above two patents, however, were found to be incompatible with copper conductors under certain conditions.
Resistors compatible with copper conductors have been found recently and are described in a copending application Ser. No. 934,269, filed Aug. 16, 1978 filed concurrently with the present application. Although these resistors have relatively low TCR values, there are many applications which require even lower TCR's.